Thanks for sharing the initiative of improving Java side Table expression DSL.
I agree as in the doc stated that Java DSL was always a "3rd class citizen" and we've run into many hand holding scenarios with our Flink developers trying to get the Stringify syntax working. Overall I am a +1 on this, it also help reduce the development cost of the Table API so that we no longer need to maintain different DSL and documentations. I left a few comments in the doc. and also some features that I think will be beneficial to the final outcome. Please kindly take a look @Timo. Many thanks, Rong On Mon, Mar 18, 2019 at 7:15 AM Timo Walther <twal...@apache.org> wrote: > Hi everyone, > > some of you might have already noticed the JIRA issue that I opened > recently [1] about introducing a proper Java expression DSL for the > Table API. Instead of using string-based expressions, we should aim for > a unified, maintainable, programmatic Java DSL. > > Some background: The Blink merging efforts and the big refactorings as > part of FLIP-32 have revealed many shortcomings in the current Table & > SQL API design. Most of these legacy issues cause problems nowadays in > making the Table API a first-class API next to the DataStream API. An > example is the ExpressionParser class[2]. It was implemented in the > early days of the Table API using Scala parser combinators. During the > last years, this parser caused many JIRA issues and user confusion on > the mailing list. Because the exceptions and syntax might not be > straight forward. > > For FLINK-11908, we added a temporary bridge instead of reimplementing > the parser in Java for FLIP-32. However, this is only a intermediate > solution until we made a final decision. > > I would like to propose a new, parser-free version of the Java Table API: > > > https://docs.google.com/document/d/1r3bfR9R6q5Km0wXKcnhfig2XQ4aMiLG5h2MTx960Fg8/edit?usp=sharing > > I already implemented an early protoype that shows that such a DSL is > not much implementation effort and integrates nicely with all existing > API methods. > > What do you think? > > Thanks for your feedback, > > Timo > > [1] https://issues.apache.org/jira/browse/FLINK-11890 > > [2] > > https://github.com/apache/flink/blob/master/flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/expressions/PlannerExpressionParserImpl.scala > >
